Hypofractionated vs. single-session Gamma Knife radiosurgery for orbital cavernous hemangiomas: A systematic review, meta-analysis, and institutional case series.

Background: Orbital cavernous hemangiomas (OCH) are rare benign vascular tumors that pose therapeutic challenges due to their proximity to critical visual structures. While surgical resection remains the standard of care, Gamma Knife radiosurgery (GKRS) has emerged as a minimally invasive alternative. However, the optimal fractionation strategy, single-session versus hypofractionated treatment, remains unclear. This review aims to evaluate the clinical and radiological outcomes of single-session versus hypofractionated GKRS for OCH through a systematic review, meta-analysis, and a complementary institutional case series.

Methods: A systematic review was conducted following PRISMA guidelines and registered with PROSPERO (registration code:1061256). Databases were searched from inception through April 2025. Eligible studies reported outcomes of GKRS for OCH using either single-session or hypofractionated treatment. Meta-analyses were performed to compare (1) the proportion of patients with tumor volume reduction, (2) the mean percentage reduction in tumor volume, and (3) the proportion of patients with improvement in visual symptoms. Risk of bias was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklists. Funnel plots and Egger's test were used to assess publication bias. Additionally, three institutional cases treated with GKRS were included to supplement the clinical context.

Results: Eleven studies comprising 117 patients were included, with an additional 3 patients from our institution. Tumor volume reduction was observed in 100 % of patients in the fractionated group and 89 % in the single-session group (p = 0.0853). The pooled mean percentage volume reduction was -2.65 % (95 % CI: -6.36 to 3.97) in the fractionated group and -2.85 % (95 % CI: -8.97 to 4.43) in the single-session group (p = 0.9572). Improvement in visual symptoms was seen in 80 % of patients in the fractionated group and 69 % in the single-session group (p = 0.4763). Funnel plots demonstrated minimal publication bias, except for a potential small-study effect in visual symptom outcomes. JBI assessment indicated moderate to high methodological quality across most studies.

Conclusion: Both single-session and hypofractionated GKRS appear to be effective and safe treatment options for OCH, with comparable clinical outcomes. Hypofractionation may offer advantages in select patients with optic nerve proximity, though current evidence does not show statistically significant differences between approaches. Single-session GKRS remains a pragmatic and effective option in anatomically favorable cases and may be complemented by adaptive or rescue fractionation strategies when tumor response is suboptimal or recurrence is observed. Prospective multicenter studies with standardized outcome reporting are needed to define optimal treatment strategies.